U.S. patent number 7,618,455 [Application Number 11/456,509] was granted by the patent office on 2009-11-17 for multiple facet joint replacement.
This patent grant is currently assigned to Facet Solutions, Inc. Invention is credited to T. Wade Fallin, E. Marlowe Goble, Robert W. Hoy.
United States Patent |
7,618,455 |
Goble , et al. |
November 17, 2009 |
Multiple facet joint replacement
Abstract
A prosthesis for the replacement of multiple diseased or
traumatized spinal facets comprises a portion that replaces at
least a bony portion of the facets to be replaced and where the
prosthesis attaches to the vertebra in a manner that does not
require attachment to, or abutment against, the lamina. Multiple
configurations of the prosthesis provide for replacement of the two
inferior facets, the two superior facets, a superior and inferior
facet, or all four facets. A method of installing the prosthesis is
provided that is comprised of the steps of resecting at least a
portion of the facets that carry the diseased or traumatized spinal
facets and attaching the prosthesis in a manner that does not
require attachment or abutment against the lamina.
Inventors: |
Goble; E. Marlowe (Alta,
WY), Fallin; T. Wade (Hyde Park, UT), Hoy; Robert W.
(Logan, UT) |
Assignee: |
Facet Solutions, Inc
(Hopkinton, MA)
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Family
ID: |
24958519 |
Appl.
No.: |
11/456,509 |
Filed: |
July 10, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060265069 A1 |
Nov 23, 2006 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10420467 |
Apr 22, 2003 |
7074237 |
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09736103 |
Dec 13, 2000 |
6565605 |
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Current U.S.
Class: |
623/17.11;
606/247; 606/246 |
Current CPC
Class: |
A61F
2/4405 (20130101); Y10S 606/91 (20130101); Y10S
606/907 (20130101) |
Current International
Class: |
A61F
2/44 (20060101) |
Field of
Search: |
;623/17.11-17.16
;606/61,70,71,72,73,290,246,247 |
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Primary Examiner: Philogene; Pedro
Attorney, Agent or Firm: Meibos; David W. Daniels; Barbara
Justin; Daniel F.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of:
U.S. application Ser. No. 10/420,467, filed Apr. 22, 2003 now U.S.
Pat. No. 7,074,237, and entitled MULTIPLE FACET JOINT
REPLACEMENT,
Which is a continuation of:
U.S. application Ser. No. 09/736,103, filed Dec. 13, 2000 now U.S.
Pat. No. 6,565,605 and entitled MULTIPLE FACET JOINT
REPLACEMENT.
The disclosures listed above are incorporated herein by reference.
Claims
The invention claimed is:
1. An implant for replacing at least a left inferior facet and a
right inferior facet of a first vertebra comprising a natural
lamina, a natural left inferior facet, and a natural right inferior
facet, the implant comprising: a left inferior articular surface
shaped to replace the natural left inferior facet; a right inferior
articular surface shaped to replace the natural right inferior
facet; and a bridge extending along a substantially straight path
between the left and right articular surfaces to couple the left
and right inferior articular surfaces together; wherein the bridge
comprises a cross sectional shape perpendicular to the path that
remains uniform over at least a portion of a length of the
path.
2. The implant of claim 1, wherein the left and right inferior
articular surfaces are attachable to the first vertebra
independently of attachment to a transverse process of the first
vertebra.
3. The implant of claim 1, wherein the cross sectional shape
remains substantially uniform along substantially all of the length
of the path.
4. The implant of claim 1, wherein the path extends substantially
medial-laterally.
5. The implant of claim 1, wherein the left and right inferior
articular surfaces are positioned substantially in-line with the
path.
6. The implant of claim 1, wherein the bridge couples the left and
right inferior articular surfaces together in such a manner that
the left and right inferior articular surfaces are non-adjustably
positionable relative to each other.
7. The implant of claim 6, wherein the left and right inferior
articular surfaces are formed as a single piece with the
bridge.
8. An implant for replacing at least a left facet and a right facet
of a first vertebra comprising a natural lamina, a natural left
facet, and a natural right facet, the implant comprising: a left
articular surface shaped to replace the natural left facet; a right
articular surface shaped to replace the natural right facet; and a
bridge extending along a substantially straight path to couple the
left and right articular surfaces together such that the left and
right articular surfaces are positioned substantially in-line with
the substantially straight path; wherein the bridge comprises a
cross sectional shape perpendicular to the path that remains
uniform over at least a portion of a length of the path.
9. The implant of claim 8, wherein the left and right articular
surfaces are attachable to the first vertebra independently of
attachment to a transverse process of the first vertebra.
10. The implant of claim 8, wherein the cross sectional shape
remains substantially uniform along substantially all of the length
of the path.
11. The implant of claim 8, wherein the path extends substantially
medial-laterally.
12. The implant of claim 8, wherein the left and right articular
surfaces comprise left and right inferior articular surfaces shaped
to articulate with left and right superior articular surfaces of a
second vertebra inferior to the first vertebra.
13. The implant of claim 8, wherein the bridge couples the left and
right articular surfaces together in such a manner that the left
and right articular surfaces are non-adjustably positionable
relative to each other.
14. The implant of claim 13, wherein the left and right articular
surfaces are formed as a single piece with the bridge.
15. An implant for replacing at least a left facet and a right
facet of a first vertebra comprising a natural lamina, a natural
left facet, and a natural right facet, the implant comprising: a
left articular surface shaped to replace the natural left facet; a
right articular surface shaped to replace the natural right facet;
and a bridge formed as a single piece with the left articular
surface and the right articular surface to couple the left and
right articular surfaces together; wherein the bridge occupies a
volume between the left and right articular surfaces; wherein at
least one of the left and right articular surfaces comprises an
inferior articular surface shaped to articulate with a superior
articular surface of a second vertebra inferior to the first
vertebra.
16. The implant of claim 15, wherein the left and right articular
surfaces are attachable to the first vertebra independently of
attachment to a transverse process of the first vertebra.
17. The implant of claim 15, wherein the bridge comprises a cross
sectional shape that remains substantially uniform along
substantially all of the length of the path.
18. The implant of claim 15, wherein the bridge extends along a
substantially straight path between the left and right articular
surfaces.
19. The implant of claim 15, wherein the path extends substantially
medial-laterally.
20. The implant of claim 15, wherein the left and right articular
surfaces comprise left and right inferior articular surfaces shaped
to articulate with left and right superior articular surfaces of a
second vertebra inferior to the first vertebra.
Description
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to surgical devices and methods to
replace a damaged, diseased, or otherwise painful spinal facet
joint.
2. Description of Related Art
Traumatic, inflammatory, metabolic, synovial, neoplastic and
degenerative disorders of the spine can produce debilitating pain
that can have severe socioeconomic and psychological effects. One
of the most common surgical interventions today is arthrodesis, or
spine fusion, of one or more motion segments, with approximately
300,000 procedures performed annually in the United States.
Clinical success varies considerably, depending upon technique and
indications, and consideration must be given to the concomitant
risks and complications. For example, it has been shown that spine
fusion decreases function by limiting the range of motion for
patients in flexion, extension, rotation, and lateral bending.
Furthermore, it has been shown that spine fusion creates increased
stresses and, therefore, accelerated degeneration of adjacent
non-fused motion segments. Additionally, pseudoarthrosis, as a
result of an incomplete or ineffective fusion, may reduce or even
eliminate pain relief for the patient. Also, the fusion device,
whether artificial or biological, may migrate out of the fusion
site.
Recently, several attempts have been made to recreate the natural
biomechanics of the spine by use of an artificial disc. Artificial
discs provide for articulation between vertebral bodies to recreate
the full range of motion allowed by the elastic properties of the
natural intervertebral disc which directly connects two opposed
vertebral bodies.
However, the artificial discs proposed to date do not fully address
the mechanics of motion of the spinal column. In addition to the
intervertebral disc, posterior elements called the facet joints
help to support axial, torsional and shear loads that act on the
spinal column. Furthermore, the facet joints are diarthroidal
joints that provide both sliding articulation and load transmission
features. The effects of their absence as a result of facetectomy
has been observed to produce significant decreases in the stiffness
of the spinal column in all planes of motion: flexion and
extension, lateral bending, and rotation. Furthermore,
contraindications for artificial discs include arthritic facet
joints, absent facet joints, severe facet joint tropism or
otherwise deformed facet joints.
U.S. Pat. No. Re. 36,758 to Fitz discloses an artificial facet
joint where the inferior facet, the mating superior facet, or both,
are covered with a cap. The cap requires no preparation of the bone
or articular surfaces; it covers and, therefore, preserves the bony
and articular structure.
The capping of the facet has several potential disadvantages. If
the facet joint is osteoarthritic, a cap will not remove the source
of the pain. Additionally, at least in the case of surface
replacements for osteoarthritis femoral heads, the capping of
articular bone ends has proven to lead to clinical failure by means
of mechanical loosening. The clinical failure is hypothesized to be
a sequela of disrupting the periosteum and ligamentum teres
femoris, both serving a nutrition delivery role to the. femoral
head, thereby leading to avascular necrosis of the bony support
structure for the surface replacement. Another potential
disadvantage is that in order to accommodate the wide variability
in anatomical morphology of the facets, not only between
individuals but also between levels within the spinal column, a
very wide variety of sizes and shapes would be required.
U.S. Pat. No. 6,132,464 to Martin discloses a spinal facet joint
prosthesis that is supported on the lamina, which is sometimes also
referred to as the posterior arch of the vertebra. Extending from
this prosthetic support structure are inferior and/or superior
blades that replace the cartilage at the facet joint. Like the Fitz
design, the Martin prosthesis generally preserves existing bony
structures and therefore does not address pathologies which affect
the bone of the facets in addition to affecting the associated
cartilage. Furthermore, the Martin invention requires a mating
condition between the prosthesis and the lamina, or the posterior
arch, that is a thin base of curved bone that carries all four
facets and the spinous process. Since the posterior arch is a very
complex and highly variable anatomic surface, it is very difficult
to design a prosthesis that provides reproducible positioning to
correctly locate the cartilage-replacing blades for the facet
joints.
Another approach to surgical intervention for spinal facets is
provided in WO9848717A1 to Villaret. While Villaret teaches the
replacement of spinal facets, the replacement is interlocked in a
manner to immobilize the joint.
Facet joint replacement in conjunction with artificial disc
replacements represent a novel solution to recreating a fully
functional motion segment that is compromised due to disease or
trauma. Together, facet joint and disc replacement can eliminate
substantially all sources of pain, return full function and range
of motion, and restore the natural biomechanics of the spinal
column. Additionally, degenerative or traumatized facet joints may
be replaced in the absence of disc replacement when the natural
intervertebral disc is unaffected by the disease or trauma.
It would therefore be an improvement in the art to provide a device
and a method for the replacement of multiple vertebral facets and a
portion of their associated bony structure so as to remove the
source of traumatic, arthritic, or other disease related pain.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a multiple vertebral
facet replacement prosthesis for a diseased or traumatized vertebra
with painful or compromised facet joints.
It is another object of the invention to provide a method of
replacing multiple vertebral facets for a diseased or traumatized
vertebra with painful or compromised facet joints.
It is yet another object of the present invention to provide a kit
of multiple facet prostheses for the convenient replacement of one
or more levels of facet joints.
In one preferred embodiment, the inferior bilateral facets of a
superior vertebra are resected at the base of the facets where they
connect to the posterior arch. Flanges are oriented relative to the
body of the prosthesis such that when the flanges are placed
against the pedicles and in a manner such that the planar surfaces
of the flanges are perpendicular to the respective axes of the
pedicle's interior bone canal, the articulating surfaces of the
inferior bilateral facet prosthesis will be properly positioned to
replicate the articulating surfaces of the natural facets. Each
flange includes a hole for the passage of a fastener to securely
attach the prosthesis to the pedicle. The fastener can be a screw,
spike, tack, staple, modular post, or the like.
Alternatively, or in addition, the superior facets of an inferior
vertebra are resected at the base of the facets where they connect
to the pedicles. As with the bilateral inferior facet prosthesis, a
bilateral superior facet prosthesis is attached to the inferior
vertebra by means-of fasteners which engage holes on mounting
flanges and the pedicles.
The fasteners or the bone contacting surfaces of the flanges may be
porous coated to promote bone ingrowth in order to achieve long
term fixation. The porous coating may carry osteoconductive agents,
such as hydroxylapatite, calcium sulfate, or demineralized bone
matrix. Alternatively, the porous coating may carry osteoinductive
agents, such as bone morphogenic proteins, including rhBMP-2 and
rhBMP-7.
Alternative embodiments of the present invention include the
replacement of different combinations of facets on a single
vertebra. One embodiment provides for the replacement of the left
inferior and left superior facets by a single prosthesis. Another
embodiment provides for the concurrent replacement of all four
facets by a single prosthesis. The four facet prosthesis can be
used in conjunction with a superior bilateral facet replacement and
an inferior bilateral facet replacement to provide a two level
replacement of facet joints. Alternatively, two of the four facet
prostheses can be used in conjunction with a superior bilateral
facet replacement and an inferior bilateral facet replacement to
provide a three level replacement of facet joints, where the middle
level facet replacement is accomplished by the two adjacent four
facet prostheses.
The present invention has numerous advantages over the prior art.
Among other things, the present invention provides for the
convenient, simultaneous replacement of multiple combinations of
facets on a single vertebra: two superior facets, two posterior
facets, two left facets, two right facets, or all four facets.
Furthermore, multiple levels of facet joints can be replaced by
selecting from a kit of multiple facet joint prostheses. Another
advantage of the present invention is a precise and tight
attachment of the prosthesis to bones, as opposed to prosthetic
surfaces that rely on mating with highly complex and variable
external surfaces of the vertebra, such as the posterior arch.
Another advantage is that the optional porous coating is placed
into interior bone spaces where porous coatings have proven to
achieve bone ingrowth for excellent long term fixation strength.
This ability to achieve bone ingrowth is uncertain for the prior
art devices that engage the external bone surfaces of the vertebra.
Yet another advantage lies in the removal of the facet bone
structure. More particularly, where the facet bone is involved in
the disease pathology or the trauma that compromised the articular
or cartilaginous surface of the facet, resection provides a means
for ensuring that all pain associated with the disease or trauma is
removed. With prior art devices, the bony structure of the facets
is generally left intact.
The above, and other, objects, features and advantages of the
present invention will become apparent from the following
description which is to be read in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a spine motion segment;
FIG. 2 is a dorsal view of a bilateral facet joint reconstructed in
accordance with the present invention;
FIG. 3 is a lateral view of the bilateral facet joint prosthesis
shown in FIG. 2;
FIG. 4 is a dorsal view of the implanted inferior bilateral facet
prosthesis shown in FIGS. 2 and 3;
FIG. 5 is an inferior view of the implanted inferior bilateral
facet prosthesis shown in FIGS. 2 and 3;
FIG. 6 is a ventral view of the inferior bilateral facet prosthesis
shown in FIGS. 4 and 5;
FIG. 7 is a dorsal view of the implanted superior bilateral facet
prosthesis shown in FIGS. 2 and 3;
FIG. 8 is a superior view of the implanted superior bilateral facet
prosthesis shown in FIGS. 2 and 3;
FIG. 9 is a ventral view of the superior bilateral facet prosthesis
shown in FIGS. 7 and 8;
FIG. 10 is a perspective view of an alternative embodiment of the
superior bilateral facet prosthesis shown in FIGS. 7 and 8;
FIG. 11 is a dorsal view of a two level facet joint
replacement;
FIG. 12 is a lateral view of the two level facet joint replacement
of FIG. 11;
FIG. 13 is a dorsal view of the implanted four facet prosthesis
shown in FIGS. 11 and 12;
FIG. 14 is a perspective view of the four facet prosthesis shown in
FIG. 13;
FIG. 15 is a perspective view of an alternative form of inferior
bilateral facet prosthesis;
FIG. 16 is a perspective view of an implanted superior and inferior
unilateral facet prosthesis; and
FIG. 17 is a perspective view of the unilateral facet prosthesis
shown in FIG. 16.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring first to FIG. 1, there is shown a superior vertebra 5 and
an inferior vertebra 10, with an intervertebral disc 15 located in
between. Vertebra 5 has superior facets 20, inferior facets 25, a
lamina (also sometimes referred to as a posterior arch) 30, a
spinous process 35, and pedicles 40. Vertebra 10 has superior
facets 45, inferior facets 50, a posterior arch 55, a spinous
process 60, and pedicles 65 (only one of which is seen in FIG.
1).
Referring now to FIG. 2, the left and right inferior facets 25 of
vertebra 5 have been resected at 70 and a bilateral inferior facet
prosthesis 75 has been attached to vertebra 5 using screw fasteners
80. Similarly, the left and right superior facets 45 of vertebra 10
have been resected at 82 (FIG. 7) and a bilateral superior facet
prosthesis 85 has been attached to vertebra 10 using screw
fasteners 90.
In FIG. 3 it can be appreciated that bilateral inferior facet
prosthesis 75 replicates the natural anatomy when compared to the
intact inferior facet 25 of vertebra 5. Furthermore, bilateral
facet prosthesis 75 extends from its attachment point in a manner
that does not require contact with, or mating to, the complex
geometry of the lamina (or posterior arch) 30. Resection surfaces
70 provide adequate clearance for bilateral inferior facet
prosthesis 75 and provide complete removal of the diseased or
traumatized natural inferior facets 25.
FIGS. 4 and 5 illustrate how the geometry of the bridge 95 of
bilateral inferior facet prosthesis 75 matches that of the
posterior arch 30 of vertebra 5 in order to provide adequate
clearance for the central foramen 100. Articular surfaces 105
articulate with the opposing superior facets 45 (or their
prosthetic replacements) of the vertebra 10.
FIG. 6 illustrates the bilateral inferior facet prosthesis 75 with
flanges 110 that abut against the pedicles 40 of vertebra 5. Bridge
95 connects the articular surfaces 105. Holes 115 allow the
attachment of bilateral inferior facet prosthesis 75 to vertebra 5
by means of screw fasteners 80. Alternatively, screw fasteners 80
could be replaced with staples, pins, tacks, anchors, modular
fixation posts, or the like. These alternative fasteners could
further include porous coatings to further enhance bony fixation,
and could also include osteoconductive or osteoinductive
substances.
In FIG. 7 it can be appreciated that bilateral superior facet
prosthesis 85 replicates the natural anatomy when compared to the
intact superior facets 45 of vertebra 10. Furthermore, bilateral
facet prosthesis 85 extends from its attachment point in a manner
that does not require contact with, or mating to, the complex
geometry of the lamina (or posterior arch) 55. Resection surfaces
82 provide adequate clearance for bilateral superior facet
prosthesis 85 and provide complete removal of the diseased or
traumatized natural superior facets 45.
FIG. 8 illustrates how the geometry of the bridge 120 of bilateral
superior facet prosthesis 85 matches that of the posterior arch 55
of vertebra 10 in order to provide adequate clearance for the
central foramen 125. Articular surfaces 130 articulate with the
opposing inferior facets of the vertebra 5.
FIG. 9 illustrates the bilateral superior facet prosthesis 85 with
flanges 135 that abut against the pedicles 65 of vertebra 10.
Bridge 120 connects the articular surfaces 130 (seen in FIG. 8 but
not seen in FIG. 9). Holes 140 allow the attachment of bilateral
superior facet prosthesis 85 to vertebra 10 by means of screw
fasteners 90.
FIG. 10 illustrates an alternative superior facet prosthesis 85A
with a bearing surface 130A that mounts to substrate 131A. The
bearing surface 130A is preferably a biocompatible polymeric
material, such as ultra high molecular weight polyethylene.
Alternately, the bearing surface 130A can be ceramic, such as
zirconia or alumina. The substrate 131A is preferably a
biocompatible metal alloy, such as an alloy of titanium, cobalt, or
iron.
FIG. 11 illustrates a superior vertebra 145, a middle vertebra 150,
and an inferior vertebra 155. Superior facet prosthesis 85
articulates with quad-facet prosthesis 160 to recreate the natural
biomechanics of the replaced facet joints. Inferior facet
prosthesis 75 articulates with quad-facet prosthesis 160 to
recreate the natural biomechanics of the replaced facet joints at
the next upper level. Thus, FIG. 11 illustrates a two level
reconstruction of facet joints. Superior facet prosthesis 85,
quad-facet prosthesis 160, and inferior facet prosthesis 75 are
each attached to bone by means of screw fasteners 165.
In the lateral view of FIG. 12, it can be appreciated that superior
facet prosthesis 85, quad-facet prosthesis 160, and inferior facet
prosthesis 75 do not encroach into the intervertebral foraminal
spaces 167 where nerve roots extend laterally from the spinal
cord.
Referring next to FIG. 13, it should be appreciated that superior
bridge 170 and inferior bridge 175 of quad-facet prosthesis 160 do
not contact any portion of vertebra 150. Mounting holes 180 (shown
in FIG. 14) are used to secure the flanges 185 against the pedicles
of vertebra 150.
In FIG. 15, an alternative inferior bilateral facet prosthesis 190
is presented. To further stabilize the implant and to counter
moments that act upon the two points of fixation into the pedicles,
a set of parallel flanges 195 extend posteriorly such that the two
flanges straddle the spinous process 35. A bolt 200 is used to
fasten the parallel flanges to the spinous process. Alternatively,
other adjunctive structural features could be added to further
stabilize the prosthesis. For example, a strut that extends, and
attaches, to the transverse process could be used to further
stabilize the prosthesis. It can be appreciated that the bridge 95
of alternative bilateral facet prosthesis 190 extends between the
left and right articular surfaces 105 (as best seen in FIG. 6) and
occupies a volume 205 between the articular surfaces, as shown in
dashed lines in FIG. 15. The volume 205 may be defined by
projecting the outline of an articular surface 105 along a straight
path between two articular suffaces. It can be appreciated that
articular surfaces 105 of different shapes or sizes would have
different outlines, thus defining volumes 205 of different shapes
or sizes.
Looking next at FIGS. 16 and 17, there is shown a superior and
inferior unilaterial facet prothesis 300. Unilaterial facet
prothesis 300 comprises a body 305 and a stem 310 extending out of
body 305. A superior element 315 extends vertically upward from
body 305, and an inferior element 310 extends vertically downward
from body 305. Unilateral facet prosthesis 300 is configured so
that when its stem 310 extends into the pedicle of vertebra 325,
superior element 315 will replace a resected superior facet, and
inferior element 320 will replace a resected inferior facet. If
desired, stem 310 could be replaced with a screw extending through
a hole in body 305 and into the pedicle.
Having described preferred embodiments of the invention with
reference to the accompanying drawings, it is to be understood that
the embodiments shown herein are by way of example and not
limitation, and that various changes and modifications may be
effected by one skilled in the art without departing from the scope
or spirit of the invention as defined in the following claims.
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